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Raspberry Pi

The Raspberry Pi is a single-board computer. You can add sensors and actuators using a wide range of devices and ecosystems, and for these lessons using a hardware ecosystem called Grove. You will code your Pi and access the Grove sensors using Python.

Setup

If you are using a Raspberry Pi as your IoT hardware, you have two choices - you can work through all these lessons and code directly on the Pi, or you can connect remotely to a 'headless' Pi and code from your computer.

Before you begin, you also need to connect the Grove Base Hat to your Pi.

Task - setup

Install the Grove base hat on your Pi and configure the Pi

Connect the Grove base hat to your Pi. The socket on the hat fits over all of the GPIO pins on the Pi, sliding all the way down the pins to sit firmly on the base. It sits over the Pi, covering it.
Decide how you want to program your Pi, and head to the relevant section below:
- Work directly on your Pi
- Remote access to code the Pi

Work directly on your Pi

If you want to work directly on your Pi, you can use the desktop version of Raspberry Pi OS and install all the tools you need.

Task - work directly on your Pi

Set up your Pi for development.

Follow the instructions in the Raspberry Pi setup guide to set up your Pi, connect it to a keyboard/mouse/monitor, connect it to your WiFi or ethernet network, and update the software.

IMPORTANT

Currently the latest Raspberry Pi OS no longer suports accessing the camera via PiCamera or any other Python library. You can read about this change in this Raspberry Pi blog post. You will need to install an older OS by downloading the Buster image from the here:

https://downloads.raspberrypi.org/raspios_armhf/images/raspios_armhf-2021-05-28/

To program the Pi using the Grove sensors and actuators, you will need to install an editor to allow you to write the device code, and various libraries and tools that interact with the Grove hardware.

Once your Pi has rebooted, launch the Terminal by clicking the Terminal icon on the top menu bar, or choose Menu -> Accessories -> Terminal
Run the following command to ensure the OS and installed software is up to date:
```
sudo apt update && sudo apt full-upgrade --yes
```
Run the following command to install all the needed libraries for the Grove hardware:
```
curl -sL https://github.com/Seeed-Studio/grove.py/raw/master/install.sh | sudo bash -s -
```
One of the powerful features of Python is the ability to install Pip packages - these are packages of code written by other people and published to the Internet. You can install a Pip package onto your computer with one command, then use that package in your code. This Grove install script will install the Pip packages you will use to work with the Grove hardware from Python.

💁 By default when you install a package it is available everywhere on your computer, and this can lead to problems with package versions - such as one application depending on one version of a package that breaks when you install a new version for a different application. To work around this problem, you can use a Python virtual environment, essentially a copy of Python in a dedicated folder, and when you install Pip packages they get installed just to that folder. You won't be using virtual environments when using your Pi. The Grove install script installs the Grove Python packages globally, so to use a virtual environment you would need to set up a virtual environment then manually re-install the Grove packages inside that environment. It's easier to just use global packages, especially as a lot of Pi developers will re-flash a clean SD card for each project.
Reboot the Pi either using the menu or running the following command in the Terminal:
```
sudo reboot
```
Once the Pi has rebooted, relaunch the Terminal and run the following command to install Visual Studio Code (VS Code) - this is the editor you will be using to write your device code in Python.
```
sudo apt install code
```
Once this is installed, VS Code will be available from the top menu.

💁 You are free to use any Python IDE or editor for these lessons if you have a preferred tool, but the lessons will give instructions based off using VS Code.
Install Pylance. This is an extension for VS Code that provides Python language support. Refer to the Pylance extension documentation for instructions on installing this extension in VS Code.

Remote access to code the Pi

Rather than coding directly on the Pi, it can run 'headless', that is not connected to a keyboard/mouse/monitor, and configure and code on it from your computer, using Visual Studio Code.

Set up the Pi OS

To code remotely, the Pi OS needs to be installed on an SD Card.

Task - set up the Pi OS

Set up the headless Pi OS.

Download the Raspberry Pi Imager from the Raspberry Pi OS software page and install it
Insert an SD card into your computer, using an adapter if necessary
Launch the Raspberry Pi Imager
From the Raspberry Pi Imager, select the CHOOSE OS button, then select Raspberry Pi OS (Other), followed by Raspberry Pi OS Lite (32-bit)

💁 Raspberry Pi OS Lite is a version of Raspberry Pi OS that doesn't have the desktop UI or UI based tools. These aren't needed for a headless Pi and makes the install smaller and boot up time faster.
Select the CHOOSE STORAGE button, then select your SD card
Launch the Advanced Options by pressing Ctrl+Shift+X. These options allow some pre-configuration of the Raspberry Pi OS before it is imaged to the SD card.
1. Check the Enable SSH check box, and set a password for the pi user. This is the password you will use to log in to the Pi later.
2. If you are planning to connect to the Pi over WiFi, check the Configure WiFi check box, and enter your WiFi SSID and password, as well as selecting your WiFi country. You do not need to do this if you will use an ethernet cable. Make sure the network you connect to is the same one your computer is on.
3. Check the Set locale settings check box, and set your country and timezone
4. Select the SAVE button
Select the WRITE button to write the OS to the SD card. If you are using macOS, you will be asked to enter your password as the underlying tool that writes disk images needs privileged access.

The OS will be written to the SD card, and once complete the card will be ejected by the OS, and you will be notified. Remove the SD card from your computer, insert it into the Pi, power up the Pi and wait for about 2 mins for it to properly boot.

Connect to the Pi

The next step is to remotely access the Pi. You can do this using ssh, which is available on macOS, Linux and recent versions of Windows.

Task - connect to the Pi

Remotely access the Pi.

Launch a Terminal or Command Prompt, and enter the following command to connect to the Pi:
```
ssh pi@raspberrypi.local
```
If you are on Windows using an older version that doesn't have ssh installed, you can use OpenSSH. You can find the installation instructions in the OpenSSH installation documentation.
This should connect to your Pi and ask for the password.

Being able to find computers on your network by using <hostname>.local is a fairly recent addition to Linux and Windows. If you are using Linux or Windows and you get any errors about the Hostname not being found, you will need to install additional software to enable ZeroConf networking (also referred to by Apple as Bonjour):
1. If you are using Linux, install Avahi using the following command:
```
sudo apt-get install avahi-daemon
```
2. If you are using Windows, the easiest way to enable ZeroConf is to install Bonjour Print Services for Windows. You can also install iTunes for Windows to get a newer version of the utility (which is not available standalone).
💁 If you cannot connect using raspberrypi.local, then you can use the IP address of your Pi. Refer to the Raspberry Pi IP address documentation for instructions on a number of ways to get the IP address.
Enter the password you set in the Raspberry Pi Imager Advanced Options

Configure software on the Pi

Once you are connected to the Pi, you need to ensure the OS is up to date, and install various libraries and tools that interact with the Grove hardware.

Task - configure software on the Pi

Configure the installed Pi software and install the Grove libraries.

From your ssh session, run the following command to update then reboot the Pi:
```
sudo apt update && sudo apt full-upgrade --yes && sudo reboot
```
The Pi will be updated and rebooted. The ssh session will end when the Pi is rebooted, so leave it for about 30 seconds then reconnect.
From the reconnected ssh session, run the following command to install all the needed libraries for the Grove hardware:
```
curl -sL https://github.com/Seeed-Studio/grove.py/raw/master/install.sh | sudo bash -s -
```
One of the powerful features of Python is the ability to install Pip packages - these are packages of code written by other people and published to the Internet. You can install a Pip package onto your computer with one command, then use that package in your code. This Grove install script will install the Pip packages you will use to work with the Grove hardware from Python.

💁 By default when you install a package it is available everywhere on your computer, and this can lead to problems with package versions - such as one application depending on one version of a package that breaks when you install a new version for a different application. To work around this problem, you can use a Python virtual environment, essentially a copy of Python in a dedicated folder, and when you install Pip packages they get installed just to that folder. You won't be using virtual environments when using your Pi. The Grove install script installs the Grove Python packages globally, so to use a virtual environment you would need to set up a virtual environment then manually re-install the Grove packages inside that environment. It's easier to just use global packages, especially as a lot of Pi developers will re-flash a clean SD card for each project.
Reboot the Pi by running the following command:
```
sudo reboot
```
The ssh session will end when the Pi is rebooted. There is no need to reconnect.

Configure VS Code for remote access

Once the Pi is configured, you can connect to it using Visual Studio Code (VS Code) from your computer - this is a free developer text editor you will be using to write your device code in Python.

Task - configure VS Code for remote access

Install the required software and connect remotely to your Pi.

Install VS Code on your computer by following the VS Code documentation
Follow the instructions in the VS Code Remote Development using SSH documentation to install the components needed
Following the same instructions, connect VS Code to the Pi
Once connected, follow the managing extensions instructions to install the Pylance extension remotely onto the Pi

Hello world

It is traditional when starting out with a new programming language or technology to create a 'Hello World' application - a small application that outputs something like the text "Hello World" to show that all the tools are correctly configured.

The Hello World app for the Pi will ensure that you have Python and Visual Studio code installed correctly.

This app will be in a folder called nightlight, and it will be re-used with different code in later parts of this assignment to build the nightlight application.

Task - hello world

Create the Hello World app.

Launch VS Code, either directly on the Pi, or on your computer and connected to the Pi using the Remote SSH extension
Launch the VS Code Terminal by selecting *Terminal -> New Terminal, or pressing CTRL+`. It will open to the pi users home directory.
Run the following commands to create a directory for your code, and create a Python file called app.py inside that directory:
```
mkdir nightlight
cd nightlight
touch app.py
```
Open this folder in VS Code by selecting File -> Open... and selecting the nightlight folder, then select OK
Open the app.py file from the VS Code explorer and add the following code:
```
print('Hello World!')
```
The print function prints whatever is passed to it to the console.
From the VS Code Terminal, run the following to run your Python app:
```
python3 app.py
```
💁 You need to explicitly call python3 to run this code just in case you have Python 2 installed in addition to Python 3 (the latest version). If you have Python2 installed then calling python will use Python 2 instead of Python 3

The following output will appear in the terminal:
```
pi@raspberrypi:~/nightlight $ python3 app.py
Hello World!
```

💁 You can find this code in the code/pi folder.

😀 Your 'Hello World' program was a success!

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